[fpc-pascal] GZip - Stream decompress only in memory

[Marcos Douglas]

On Mon, Sep 5, 2016 at 4:43 PM, Marcos Douglas <md at delfire.net> wrote:
> On Mon, Sep 5, 2016 at 4:33 PM, Michael Van Canneyt
> <michael at freepascal.org> wrote:
>>
>> What is the stream content ? TGZFile or simply compressed ? If it is
>> TGZFile, then the header must be skipped before uncompressing data.
>
> Simply compressed.
> The example is using a file, but the real app uses streams in memory.
>
> I can't use TBase64DecodingStream either because it not implements Seek method:
>
> function TBase64DecodingStream.Seek(Offset: Longint; Origin: Word): Longint;
> begin
>   // TODO: implement Seeking in TBase64DecodingStream
>   raise EStreamError.Create('Invalid stream operation');
> end;

Ok, now I understand how TBase64DecodingStream works.
The code below is working.

=== begin ===
var
  Decoder: TBase64DecodingStream;
  F: TFileStream;
  Src, Dest: TMemoryStream;
begin
  F := TFileStream.Create('result.txt', fmOpenRead);
  Decoder := TBase64DecodingStream.Create(F);
  Src := TMemoryStream.Create;
  Dest := TMemoryStream.Create;
  try
    Src.CopyFrom(Decoder, Decoder.Size);
    if ZUncompressStream(Src, Dest) then
      Dest.SaveToFile('content.txt');
  Finally
    F.Free;
    Src.Free;
    Dest.Free;
    Decoder.Free;
  end;
end;
=== end ===

Regards,
Marcos Dougas